Pressure relief means for oil circuit breaker tanks



y 1939. H. J. LlNGAL 2,158,293

PRESSURE RELIEF MEANS FOR OIL CIRCUIT BREAKER TANKS Filed Oct. 9, 1937 WITNESSES: INVENTOR 66/7 aw/GA [ya ATTORN E Patented May 16, 1939 UNITED STATES PATENT OFFICE PRESSURE RELIEF MEANS FOR. OIL CIRCUIT I BREAKER TANKS Pennsylvania Application October 9, 1937, Serial No. 168,215

4 Claims.

The invention relates in general to pressure relief means for protecting containers from damage due to the development of high internal pressures, and more particularly to pressure relief means for oil circuit breaker tanks or other tanks containing electrical apparatus and an insulating liquid.

Considerable difliculties have been experienced in connection with oil circuit breakers due to the development of dangerously high internal pressures within the enclosing tank resulting from arcing, explosions, and other causes. Under certain conditions, the internal pressure develops relatively slowly, while under other conditions, it develops extremely rapidly. In either case, damage to the tank or apparatus will result unless some means is provided for relieving the internal pressure before it reaches a dangerous value. Various means have been proposed for relieving this internal pressure, but none have proved entirely satisfactory. One arrangement has been to provide the tank with an opening covered by a closure cap which is directly biased to closed position by spring means engaging the cap. This arrangement functions satisfactorily for slowly developing pressures, but fails to protect the tank in the case of extremely rapidly developed pressures. The failure in the case of rapidly developing pressure is due to the fact that the resistance to opening caused by the spring means increases rapidly as the cap moves toward open position. Hence, when pressure develops extremely rapidly, the cap does not open fast enough to relieve the pressure.

An object of the invention is the provision of an improved pressure relief means for a container which is operable to protect the container from damage due to high internal pressures whether the pressure develops slowly or very rapidly.

Another object of the invention is the provision of an oil circuit breaker tank embodying an improved pressure relief means for automatically relieving internal pressures of more than a predetermined value developed within the tank.

Another object of the invention is the provision of a container or tank having a pressure relief opening, with a closure for the opening and a novel mechanism for biasing the closure to closed position which offers a substantially uniform resistance to opening throughout its working stroke so as to relieve very rapid rises in pressure within the tank instantly and to relieve gradual rises in pressure at a predetermined pressure, and which automatically restores the closure to closed position after the pressure is relieved.

Another object of the invention is the provision of an improved pressure relief means for a container for protecting the container from damage by high internal pressures, which is simple, reliable in operation, inexpensive to produce and which occupies a minimum amount of space.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will best be understood from the following detailed description of a preferred embodiment thereof when read in connection with the accompanying drawing, in which:

Figure 1 is a fragmentary view, partly in section, of an oil circuit breaker tank embodying a pressure relief means constructed in accordance with the invention; and

Fig. 2 is an enlarged fragmentary bottom plan View of the pressure relief means illustrated in Fig. 1.

Referring to the drawing and particularly to Fig. 1 thereof, there is shown an oil circuit breaker indicated generally at 3. The structural details of the circuit breaker, including its contact means and operating mechanism, are not an important part of the present invention and hence only so much of the circuit breaker structure is shown as is considered necessary for a complete understanding of the invention. The circuit breaker comprises in general a liquid-tight container or tank 5 of suitable material and a cover I removably mounted thereon which supports a pair of insulating conductor bushings 9 and II. Relatively movable contacts (not shown) are submerged in a body of insulating liquid, such as oil, within the tank 5, and the contact means is adapted to be operated by a suitable operating mechanism (not shown). The cover 1 is removably mounted on the tank by a plurality of bolts l3, and the joint between the cover I and the tank 5 is sealed by a suitable gasket l5 to prevent the entrance of moisture into the tank. The insulating bushings 9 and II, which serve to house and insulate the lead-in conductors for the circuit breaker, are mounted on the cover 1 by means of the flanged collars I! which are secured to the cover by means of the bolts I9.

In order to protect the tank and apparatus from damage due to dangerous internal pressures developed within the tank by arcing and other causes, there is provided a pressure relief means indicated generally at ill. The cover if of the tank is provided with a pressure relief opening 23, in which is mounted a collar 25 secured in the opening by either mechanical means or welding. A closure cap Ell is seated on the upper edge of the collar 25 and normally serves to close the pressure relief opening. The closure cap 21 is provided with an annular recess in which is disposed a gasket 23 for engaging the upper edge of the collar 25' to seal the pressure relief opening against the entrance of moisture when the closure cap is in closed position. The cap 2'? is mounted on the collar 25 for limited vertical movement between a closed and an open position and guided in its movement by means of a plurality of guide bolts 3|. The upper ends of the guide bolts 39 are threaded in suitable openings provided therefor in the closure cap Bl. The body portions of the guide bolts 35 extend through openings provided therefor in the guide brackets 33 which extend inwardly from the lower portion of the collar 25. The brackets may be formed integral with the collar 25 or secured thereto by welding or by mechanical means. The lower ends of the guide bolts 3! are threaded for receiving the castle nuts 35, which serve to limit upward or opening movement of the closure cap 2? by engaging the guide brackets 33.

The closure cap 2'! is biased to closed position with a predetermined force by a mechanism including a tension spring Bl and a mechanical link age which connects the spring 3i to the cap 21. The collar 25 is provided with a pair of spaced parallel ribs 4! which serve to support a part of the linkage 39. The linkage 39 comprises a yoke-shaped lever 43 which is pivotally mounted intermediate its ends on the ribs ii of the collar 25 and a curved link 45 which is pivotally connected at its lower end to the lower end of lever 43, and at its upper end to the closure cap 27. The lever 43 and the link 45 form a toggle which assumes a collapsed position when the closure cap 2i is in closed position, as shown in Fig. 1, and unfolds when the cap 2? moved up wardly. The lever 43 has a pair of spaced parallel outer legs 59 (Fig. 2) and a pair of spaced parallel inner legs 55 extending from its transverse body portion and formed integral therewith. The lever 33 is pivotally mounted on the ribs M of the collar 25 by means of a transverse pivot pin ll, which extends through aligned openings provided therefor in the ribs ll and in the legs 49 and ii of the lever The link 35 is pivotally connected by means of a pin 53 at its upper end to a pair of spaced parallel ribs (Fig. 2) formed integral with the closure cap 21, the upper end of the link 45 extending in the space between the ribs 55. The lower end of the link l -.5 extends between the lower ends of the inner legs of lever 63 and is pivotally connected to the lever 43 by means of a transverse pivot pin iii which extends through openings provided therefor in the lower end of the link and in the legs iii of the lever 43.

One end of the spring 3'8 is anchored to a lug 59 secured to the cover l and its other end is connected to a stud 59 which extends from one side of the lever i3 adjacent its upper end. The spring ill biases the lever in a counter-clockwise direction about its pivot axis exerting a downward pull on the link b restrain the closure cap 27 in its closed position, as shown in Fig. l.

The above-described linkage 39 for connecting the spring 31 to the closure cap 21 causes the spring to exert substantially the same biasing force on closure cap 21 in every position of the cap 2?, even though the reactive force of the spring 3'5 increases rapidly as it is stretched during opening movement of the closure cap 2?. This results from the fact that as the closure cap 2"; moves upwardly toward open position, the lever d3 is rotated in a clockwise direction about its pivot axis i-l by the link 45 which is connected to the cap 21. As the lever 43 rotates in a clockwise direction, the line of action of the spring ill is moved closer to the pivot axis 01" the lever 43, shortening the moment arm of the spring acting on the lever 43. Thus even though the reactive force of the spring 37 increases as the closure cap 2? moves upwardly toward full open position, the moment arm of the spring on the lever 43 is automatically decreased. It will also be noted that the moment arm of the closure cap 2i acting on the lever 43 increases as the cap moves toward full open position. As a result of these actions, the biasing force applied to the closure cap 21 by the spring 37 is substantially the same in every position of the cap so that the resistance to opening movement of the closure cap substantially uniform throughout its working stroke. By changing the effective moment arms of the lever 43, almost any desired resistance to opening characteristic of the closure cap 27] may be secured. The linkage 39 may be ar-- ranged so that the closure cap ofiers a decreasing resistance to opening movement as it is moved toward full open position.

The ribs H of the collar 25 are notched as indicated at 63, Fig. l, to accommodate the body portion 52 of the lever 43 when the closure cap El is in its closed position. The castle nuts 35 are adjusted so that they engage the guide brackets 33 at substantially the same time the body portion 52 of the lever 43 engages the lower edges of the ribs 46, to limit opening movement of the closure cap 27.

The initial tension of the spring 3'! is such that the closure cap 2'! opens when the pressure within the tank reaches a predetermined value below the dangerous value. If desired, the initial tension of the spring 37 may be made adjustable in any well known manner, as for example, by mounting the bracket 53 so that it is adjustable toward or away from the closure cap 21.

The operation of the pressure relief means 2| is briefly as follows: When the pressure developed within the tank 5, as a result of arcing or other causes, reaches a predetermined value, the closure cap 27 is moved upwardly thereby to uncover the pressure relief opening 23 and thus relieve the internal pressure. As the closure cap 2'11 moves upwardly, the link 45, which is connected to the cap, moves upwardly and partially rotates in a clockwise direction about its pivot axis 53. The upward and clockwise movement of the link 45 moves the lever 43 in a clockwise direction against the bias of the spring 31. The toggle formed by the lever 43 and the link 45 thus unfolds as the closure cap moves toward its full open position. As the lever 43 is moved in a clockwise direction, the moment arm of the spring 3'! acting on the lever 43 is decreased while the moment arm of the closure cap acting on the lever is at the same time increased. This change in the above-mentioned moment arms compensates for the increased reactive force of the spring 31, which is stretched as the lever 43 is rotated, so that the biasing force transmitted to the closure cap 21 by the linkage 39 is substantially uniform throughout the working stroke of the closure cap. If the predetermined pressure is developed gradually, the closure cap begins to open as soon as the predetermined pressure is reached. In such instance the closure cap 21v opens a sufiicient amount to relieve the internal pressure, after which it is returned to closed position by the biasing action of the spring 31. If the pressure develops extremely rapidly, the closure cap is moved to its full open position substantially instantaneously due to the fact that its resistance to opening movement is the same throughout its working stroke, 1. e., to say it offers the same resistance to opening adjacent its full open position as in the beginning of its opening movement. Thus the pressure relief means not only serves to protect the casing and apparatus when the pressure develops slowly, but also when the pressure develops extremely rapidly. After the pressure is relieved, the closure cap is returned to closed position as shown in Fig. 1, to seal the opening 23.

While the invention has been disclosed in connection with an oil circuit breaker tank, it will be readily understood that it is equally applicable to any form of container or casing within which dangerous internal pressures may be developed.

Various changes in the structural details of the invention may be made without departing from the spirit of the invention. It is desired,

, therefore, that the language of the appended claims be given the broadest reasonable construction permissible in the light of the prior art.

I claim as my invention:

1. In a liquid break circuit breaker, relatively movable contact means, a tank for enclosing said contact means containing a body of insulating liquid, said tank having a pressure relief opening above the level of the liquid, a closure for said opening movable from a closed position closing said opening to an open position for relieving pressure developed within said tank, means disposed inside of said tank for biasing said closure to closed position with a predetermined and substantially constant force throughout the range of movement of said closure, said means comprising a lever pivoted intermediate its ends on a fixed support in said tank directly beneath said opening, a spring in said tank anchored at one end and connected at its other end to one end of said lever above the pivot axis of said lever, and a link inside said tank pivotally connecting the other end of said lever to said closure, the points of connection of said link to said closure and to said lever being disposed in a line which is relatively close to the pivot axis of said lever when said closure is in closed position.

2. In a liquid break circuit breaker, relatively movable contact means, a tank for enclosing said contact means containing a body of insulating liquid, said tank having a pressure relief opening above the level of the liquid, a closure for said opening movable from a closed position closing said opening to an open position for relieving pressure developed within said tank, means disposed inside of said tank for biasing said closure to closed position with a predetermined and substantially constant force throughout the range of movement of said-closure, said means comprising a lever pivoted intermediate its ends on a fixed support in said tank directly beneath said opening, a spring in said tank anchored at one end and connected at its other end to one end of said lever above the pivot axis of said lever, and a link inside said tank pivotally connecting the other end of said lever to said closure, the points of connection of said link to said closure and to said lever being disposed in a line which is relatively close to the pivot axis of said lever when said closure is in closed position, said spring extending substantially parallel to and relatively close to one wall of said tank.

3. In an electrical device, a tank containing electrical apparatus and a body of insulating liquid, a cover removably mounted on the top of said tank, said cover having a pressure relief opening, a closure for said opening movable from a closed position closing said opening to an open position for relieving pressure developed in said tank, means disposed inside said tank and cover for biasing said closure to closed position with a predetermined and substantially constant force throughout the range of movement of said closure comprising a lever pivotally mounted intermediate its ends directly beneath said opening on a support carried by said cover, a tension spring anchored at one end to the inside of said cover and connected to one end of said lever above the pivot axis of said lever, and a link pivotally connecting the opposite end of said lever to said closure, the line joining the points of connection of said link to said closure and to said lever being disposed relatively close to the fixed pivot axis of said lever when the closure is in closed position.

4. In an electrical device, a tank containing electrical apparatus and a body of insulating liquid, a cover removably mounted on the top of said tank, said cover having a pressure relief opening, a closure for said opening movable from a closed position closing said opening to an open position for relieving pressure developed in said tank, means disposed inside said tank and cover for biasing said closure to closed position with a predetermined and substantially constant force throughout the range of movement of said closure comprising a lever pivotally mounted intermediate its ends directly beneath said opening on a support carried by said cover, a tension spring anchored at one end to the inside of said cover and connected to one end of said lever above the pivot axis of said lever, and a link pivotally connecting the opposite end of said lever to said closure, the line joining the points of connection of said link to said closure and to said lever being disposed relatively close to the fixed pivot axis of said lever when the closure is in closed position, and said spring extending substantially parallel to and relatively close to said cover.

HARRY J. LINGAL. 

